The present invention relates to an apparatus for mechanically finishing workpieces such as spoons, ladles, pipes, cocks and other metallic parts for waterworks, gas cocks, watch cases, levers, brake arms, cranks for bicycles, etc. to provide them with uniformly polishing surfaces.
It has been known that a workpiece secured on a spindle may be moved to be polished at a high speed in dry media covered with abrasive grain particles and fatty substances in a polishing bath by making said spindle perform orbital revolution and on-the-axis rotation in forward and reverse directions (U.S. Pat. No. 2,899,777).
However, this conventional type of the polishing apparatus cannot, in some cases, uniformly polish the whole surfaces of workpieces. FIG. 1 shows workpiece "c" which is fixed on spindle "a" with jig "b". In the figure, spindle "a" revolves (orbitally) in the direction of arrowhead "R" or in a reverse direction to said arrowhead direction "R" and rotates (around its own axis) in direction "r" or in a reverse direction to said direction "r", thereby workpiece "c" is forced to revolve and rotate together with the orbital revolution and own rotation of the spindle "a". Since workpiece "c" is fixed on spindle "a", the relative position of workpiece "c" in reference to spindle "a" does not vary and therefore there may be a difference in the degree of polishing finish between the upper part and the lower part of workpiece "c" and between the internal surface and the external surface of workpiece "c" (an opposite surface to spindle "a" and a rear surface of said opposite surface to spindle "a").